From 2d4b8549c6302728c52cab824cea1c991fe5d2a9 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Sun, 20 May 2018 08:56:29 +0200
Subject: [PATCH] - per-sector plane rendering needs to be disabled when
 processing a line portal with hardware that has no working clip plane
 support.

In this case there are no means to discard the parts of the rendered sectors that lie behind the portal so it should only render the parts that are flagged as visible.
---
 src/gl/renderer/gl_renderstate.cpp |  2 +-
 src/gl/renderer/gl_renderstate.h   | 11 +++++++++++
 src/gl/scene/gl_flats.cpp          |  4 ++--
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/gl/renderer/gl_renderstate.cpp b/src/gl/renderer/gl_renderstate.cpp
index 305a5177cc..a0a1c5cc81 100644
--- a/src/gl/renderer/gl_renderstate.cpp
+++ b/src/gl/renderer/gl_renderstate.cpp
@@ -62,7 +62,7 @@ static void matrixToGL(const VSMatrix &mat, int loc)
 void FRenderState::Reset()
 {
 	mTextureEnabled = true;
-	mClipLineEnabled = mSplitEnabled = mBrightmapEnabled = mFogEnabled = mGlowEnabled = false;
+	mClipLineShouldBeActive = mClipLineEnabled = mSplitEnabled = mBrightmapEnabled = mFogEnabled = mGlowEnabled = false;
 	mColorMask[0] = mColorMask[1] = mColorMask[2] = mColorMask[3] = true;
 	currentColorMask[0] = currentColorMask[1] = currentColorMask[2] = currentColorMask[3] = true;
 	mFogColor.d = -1;
diff --git a/src/gl/renderer/gl_renderstate.h b/src/gl/renderer/gl_renderstate.h
index 1db6602a57..8aa4d00938 100644
--- a/src/gl/renderer/gl_renderstate.h
+++ b/src/gl/renderer/gl_renderstate.h
@@ -81,6 +81,7 @@ class FRenderState
 	bool mGlowEnabled;
 	bool mSplitEnabled;
 	bool mClipLineEnabled;
+	bool mClipLineShouldBeActive;
 	bool mBrightmapEnabled;
 	bool mColorMask[4];
 	bool currentColorMask[4];
@@ -201,6 +202,11 @@ public:
 		return mClipLineEnabled;
 	}
 
+	bool GetClipLineShouldBeActive()
+	{
+		return mClipLineShouldBeActive;
+	}
+
 	void SetClipHeight(float height, float direction);
 
 	void SetNormal(FVector3 norm)
@@ -326,6 +332,11 @@ public:
 				glDisable(GL_CLIP_DISTANCE0);
 			}
 		}
+		else
+		{
+			// this needs to be flagged because in this case per-sector plane rendering needs to be disabled if a clip plane is active.
+			mClipLineShouldBeActive = on;
+		}
 	}
 
 	void EnableBrightmap(bool on)
diff --git a/src/gl/scene/gl_flats.cpp b/src/gl/scene/gl_flats.cpp
index 39ab921b49..1810508bcc 100644
--- a/src/gl/scene/gl_flats.cpp
+++ b/src/gl/scene/gl_flats.cpp
@@ -167,7 +167,7 @@ void FDrawInfo::ProcessLights(GLFlat *flat, bool istrans)
 {
 	flat->dynlightindex = GLRenderer->mLights->GetIndexPtr();
 
-	if (flat->sector->ibocount > 0 && !gl_render_subsectors)
+	if (flat->sector->ibocount > 0 && !gl_render_subsectors && !gl_RenderState.GetClipLineShouldBeActive())
 	{
 		SetupSectorLights(flat, GLPASS_LIGHTSONLY, nullptr);
 	}
@@ -214,7 +214,7 @@ void FDrawInfo::DrawSubsectors(GLFlat *flat, int pass, bool processlights, bool
 	if (gl.legacyMode) processlights = false;
 
 	auto vcount = flat->sector->ibocount;
-	if (vcount > 0 && !gl_render_subsectors)
+	if (vcount > 0 && !gl_render_subsectors && !gl_RenderState.GetClipLineShouldBeActive())
 	{
 		if (processlights) SetupSectorLights(flat, GLPASS_ALL, &dli);
 		drawcalls.Clock();